A stent is an elongated device used to support an intraluminal wall. In the case of a stenosis, a stent provides an unobstructed conduit through a body lumen in the area of the stenosis. Such a stent may also have a prosthetic graft layer of fabric or covering lining the inside and/or outside thereof. Such a covered stent is commonly referred to in the art as an intraluminal prosthesis, an endoluminal or endovascular graft (EVG), or a stent-graft. A stent-graft may be used, for example, to treat a vascular aneurysm by removing the pressure on a weakened part of an artery so as to reduce the risk of rupture. The term “endoluminal device” is often used to refer to any device implanted in a lumen, including stents, stent-grafts, vena cava filters, and the like.
Typically, an endoluminal device, such as a stent-graft deployed in a blood vessel at the site of a stenosis or aneurysm, is implanted endoluminally, i.e. by so-called “minimally invasive techniques” in which the device, restrained in a radially compressed configuration by a sheath or catheter, is delivered by a delivery system or “introducer” to the site where it is required. The introducer may enter the body from an access location remote from the treatment site, such as through the patient's skin, or by a “cut down” technique in which the entry blood vessel is exposed by minor surgical means. The term “proximal” as used herein refers to portions of the stent or delivery system relatively closer to the end of the delivery system that is remote from the treatment site, whereas the term “distal” is used to refer to portions farther from the end that is remote from the treatment site.
When the introducer has been advanced into the body lumen to the deployment location, the introducer is manipulated to cause the endoluminal device to be ejected from the surrounding sheath or catheter in which it is restrained (or alternatively the surrounding sheath or catheter is retracted from the endoluminal device), whereupon the endoluminal device is expanded to a predetermined diameter at the deployment location, and the introducer is withdrawn. Stent expansion may be effected by spring elasticity, balloon expansion, or by the self-expansion of a thermally or stress-induced return of a memory material to a pre-conditioned expanded configuration.
Stent-grafts are known in the art having a “wind-sock” design whereby the graft is attached to the stent at only an upstream location on the stent, so that as the stent is deployed, endoluminal fluid can continue to flow between the stent and the graft, while the graft is suspended like a wind sock. Such designs avoid the pressure of obstructed blood flow during deployment that may cause the prosthesis to migrate away from its intended location or become longitudinally compressed. An exemplary such stent-graft design is described in U.S. Pat. No. 5,954,764 to Juan Parodi, incorporated herein by reference, which also describes an exemplary device for deploying such a stent-graft design. Another deployment system for such a stent-graft design is described in U.S. patent application Ser. No. 09/337,120, titled LOW PROFILE DELIVERY SYSTEM FOR STENT AND GRAFT DEPLOYMENT AND METHOD FOR DEPLOYMENT, by Carl E. Yee, filed Jun. 21, 1999, assigned to the assignee of the present invention, and incorporated herein by reference.
The standard wind-sock stents known in the art, however, have drawbacks related to precision of deployment, stent flexibility once deployed, and complexity of the introducers used for deploying them. Thus, there is still a need in the art for improved stent-graft designs that minimize disruption of fluid flow during deployment, but also provide advantages over designs currently known in the art.